Download Water Properties and Molecular Structure File

Name___________________________ Block_______
Water Properties and Molecular Structure
1.
In the space to the right, draw a
water molecule and label the
following:
 Hydrogen
 Oxygen
 Positive partial
charge
 Negative partial
charge
2. Pick up a couple water molecules and allow them to stick together. Draw
a diagram or describe where they come in contact with each other.
a. State the type of bond that forms between water molecules:
3. Take one water molecule and make as many connections as you can to
other water molecules. Draw the structure that you have (2D is fine, used
dashed lines to show hydrogen bonds)
a. State how many hydrogen bonds one water molecule can form.
Thermal Properties
4. Water is densest at 4 degrees Celsius. Water is in a liquid state at this
point. With your magnets try to get the water molecules as close together
as possible and move them around with your hands. See if you can feel
the hydrogen bonds breaking and forming as the molecules move past
each other.
5. When water freezes it locks into position into an organized structure with
each molecule making as many connections as possible (see number 3).
With your partner, use ALL of your molecules to model water in it’s solid
state, ice. Describe this structure.
6. Model the ice melting back into liquid. As you move the water molecules
apart imagine that they are not charged and have no magnets. Does it
take less energy or more energy to “melt” ice that has dipolar molecules?
a. Explain why ice (and water) has such a high melting point (and
boiling point)
7. Sweating is an efficient way of cooling the body. Water in liquid form
heats up on the surface of the skin, then changes to a gas as it evaporates.
Using water’s unique properties explain why sweating helps cool tissues
in the body.
8. Methane is a small molecule, similar in molecular weight to water.
However methane is non-polar and does not form hydrogen bonds.
Below is a table comparing the properties of water and methane:
Property
Formula
Molecular Mass
Specific Heat Capacity
Melting Point
Boiling Point
Methane
CH4
16
2.2 J per g per °C
-182 °C
-160 °C
Water
H2O
18
4.2 J per g per °C
0 °C
100 °C
a. Compare the melting and boiling points of water and methane.
b. Explain the difference seen in the specific heat capacity between
methane and water.
c. Is methane hydrophilic or hydrophobic?
Adhesion and Cohesion
9. Arrange your water molecules into a long chain. Is this the adhesive or
cohesive property of water?
10. Attach your long chain to the magnet. Is this the adhesive or cohesive
property of water?
11. The magnet represents a charged surface. Charged surfaces include
materials like glass and wood. Paper towels are made from ground up
wood that makes them so good at absorbing water. Get a beaker and a
paper towel strip. Fill your beaker with water and dip just one edge of the
paper towel into water.
a. Describe what you observe
b. Explain how water can move up the xylem in plants using the
terms adhesion and cohesion
c. Is wood (and paper) a hydrophobic or hydrophilic material? Use
your observation to explain your answer.
Universal Solvent
12. You should have a couple ions. Ions are charged particles. When a
positive and negative ions come together they’re called a salt. You have
table salt, NaCl or sodium chloride. The Na portion of the salt is blue, the
Cl portion of the salt is green. See how your water molecules attach to the
ions.
a. Draw a Na ion and a water molecule showing which part of the
molecule is attracted to Na
b. Draw a Cl ion and a water molecule showing which part of the
molecule is attracted to the Cl
c. Does Na and Cl have a positive or negative charge? Label your
drawing with the charges of Na and Cl.
d. Explain why water dissolves (or breaks up) charged molecules
and ions so well.
e. The following table lists common substances needed by the body.
These substances are carried in the blood in order to deliver the
substances to the cells that require them. Blood consists of several
components; red blood cells, white blood cells, platelets and
plasma. Do some research and describe how these molecules are
transported in the blood.
Substance
Sodium Chloride
Amino Acids
Glucose
Oxygen
Polar or Nonpolar
Method of Transport